Generally, after an optical disc is loaded into the optical disc drive, a start-up procedure is executed. In the start-up procedure, the optical disc is rotated by the optical disc drive, and an optical pickup head of the optical disc drive emits laser light. The laser light is focused on a rotating optical disc, and the light reflected by the optical disc is detected to realize the type of the optical disc and associated controlling parameters. Generally, the common optical discs include read-only, write-once or rewritable compact discs (CDs), digital versatile discs (DVDs) or Blu-ray discs.
In addition, after the optical disc is loaded and before the start-up procedure, the optical disc drive needs to execute a process of stopping the spindle motor and an action of moving a sled to a home position (also referred as a move-sled-home action). After the rotation of the spindle motor is stopped and the sled is moved to the home position, the start-up procedure of the optical disc drive is executed.
FIG. 1A is a schematic view illustrating the internal configurations of a conventional optical disc drive. As shown in FIG. 1A, the optical disc drive comprises a spindle motor 20, a guiding rail 30, a sled 40, a limit switch 50, a spiral guiding rod 60 and a sled motor 70. In addition, an optical pickup head 42 is supported on the sled 40 for emitting laser light, which is focused on an optical disc (as indicated by a dotted line).
When the optical disc is loaded into the optical disc drive, the optical disc is disposed above the spindle motor 20 and driven to rotate by the spindle motor 20. Moreover, the spiral guiding rod 60 is rotated by the sled motor 70. The sled 40 is supported by the guiding rail 30 and the spiral guiding rod 60. By changing the rotating direction of the sled motor 70, the sled 40 is moved back and forth along the radial direction of the optical disc.
FIG. 1B is a schematic view illustrating a procedure of moving the sled to a home position by a conventional optical disc drive. As known, during the move-sled-home action, the sled 40 is driven by the sled motor 70 and moved toward the inner track of the optical disc. The position of the innermost track is also defined as a sled-home position. Until the sled 40 is moved to the innermost track of the optical disc, the limit switch 50 is touched and triggered by the sled 40. In other words, the optical disc drive could determine whether the sled 40 is moved to the sled-home position according to the status of the limit switch 50.
For most optical disc drives, the limit switch is usually omitted in order to reduce the fabricating cost. In a case that the limit switch is omitted, the optical disc drive cannot determine whether the sled is moved to the sled-home position according to the status of the limit switch.
For executing the move-sled-home action in the case that no limit switch is included in the optical disc drive, a constant voltage is transmitted to the sled motor within a sled-home duration when each move-sled-home action is executed. Since the optical disc drive fails to realize the actual position of the sled before the move-sled-home action starts, the constant voltage and the sled-home duration are set to allow the sled to be moved from the outermost track to the innermost track of the optical disc. Moreover, since no limit switch is included in the optical disc drive, the sled will be in contact with the spindle motor when the sled is moved to exceed the sled-home position.
However, when the move-sled-home action is executed by the optical disc drive, the sled is not always located at the outermost track of the optical disc. As such, the sled and the spindle motor usually collide with each other during the move-sled-home action. Even if the sled is very close to the innermost track of the optical disc before the move-sled-home action starts, the sled-home duration is fixed. That is, this conventional method is time-consuming. Since the constant voltage is continuously received by the sled motor after the spindle motor is collided by the sled, the spiral guiding rod and the sled are readily damaged.
Therefore, there is a need of providing a controlling method and a controlling device for moving a sled to a home position by an optical disc drive in order to obviate the drawbacks encountered from the prior art.